I used this recipe, but instead of the brown sugar icing I did a streusel topping.
1/2 C. packed light brown sugar
1 1/2 tsp ground cinnamon
1 (18.5 oz) box white or yellow cake mix (I used white)
1 (6 oz) package vanilla pudding mix
1 C. sour cream (or you can use plain yogurt)
3/4 C. hot water
1/3 C. vegetable oil
1 tsp. vanilla extract
1/2 C mini chocolate chips
1/4 C, flour
1/2 C. brown sugar
6 TBS cold butter
1 tsp. cinnamon
1/4 tsp. salt
Preheat the oven to 350 degrees
Combine the brown sugar and cinnamon in a small mixing bowl, mix well and set aside. In a large bowl combine the cake mix,pudding mix, sour cream and hot water and mix well. It should be thick. Beat in the eggs, oil and vanilla extract until it is smooth.
Grease and lightly flour a 9x13 baking pan.
Pour half of the mixture into the pan. Sprinkle all of the brown sugar and cinnamon over the batter, then sprinkle with the chocolate chips. Carefully spread the remaining batter over the top of it all. With a bitter knife swirl the cake and brown sugar mixture.
For the streusel mix the cinnamon, brown sugar, flour, and salt in a small mixing bowl. Cut in the butter with a pastry blender until it is well incorporated and is in little clumps/crumble.
Sprinkle the top with your streusel mix.
Bake for 35-40 minutes, or until a toothpick inserted in the center comes out clean.